A Review of the Mass Measurement Techniques proposed for the Large Hadron Collider

We review the methods which have been proposed for measuring masses of new particles at the Large Hadron Collider paying particular attention to the kinematical techniques suitable for extracting mass information when invisible particles are expected.Comment: 72 pages - in form to be published in JPhys

Precision Determination of Invisible-Particle Masses at the CERN LHC: II

We further develop the constrained mass variable techniques to determine the mass scale of invisible particles pair-produced at hadron colliders. We introduce the constrained mass variable M_3C which provides an event-by-event lower bound and upper bound to the mass scale given the two mass differences between the lightest three new particle states. This variable is most appropriate for short symmetric cascade decays involving two-body decays and on-shell intermediate states which end in standard-model particles and two dark-matter particles. An important feature of the constrained mass variables is that they do not rely simply on the position of the end point but use the additional information contained in events which lie far from the end point. To demonstrate our method we study the supersymmetric model SPS 1a. We select cuts to study events with two Neutralino_2 each of which decays to Neutralino_1, and two opposite-sign same-flavor (OSSF) charged leptons through an intermediate on-shell slepton. We find that with 300 fb^-1 of integrated luminosity the invisible-particle mass can be measured to M=96.4 +/- 2.4 GeV. Combining fits to the shape of the M_3C constrained mass variable distribution with the max m_ll edge fixes the mass differences to +/- 0.2 GeV.Comment: 13 pages, 10 figure

Re-weighing the evidence for a Higgs boson in dileptonic W-boson decays

We reconsider observables for discovering and measuring the mass of a Higgs boson via its di-leptonic decays: H --> WW* --> l nu l nu. We define an observable generalizing the transverse mass that takes into account the fact that one of the intermediate W-bosons is likely to be on-shell. We compare this new variable with existing ones and argue that it gives a significant improvement for discovery in the region m_h < 2 m_W.Comment: 3 pages, 2 figures. Changes in v2: (i) implemented a model of detector smearing, (ii) switched LHC simulation from 14 TeV to 7 TeV running, (iii) presenting results for 10 rather than 3 inverse femtobarns, (iv) corrected a typo in Fig 2 legend. Changes in v3: included published erratu

The Precision Determination of Invisible-Particle Masses at the LHC

We develop techniques to determine the mass scale of invisible particles pair-produced at hadron colliders. We employ the constrained mass variable m_2C, which provides an event-by-event lower-bound to the mass scale given a mass difference. We complement this variable with a new variable m_2C,UB which provides an additional upper bound to the mass scale, and demonstrate its utility with a realistic case study of a supersymmetry model. These variables together effectively quantify the `kink' in the function Max m_T2 which has been proposed as a mass-determination technique for collider-produced dark matter. An important advantage of the m_2C method is that it does not rely simply on the position at the endpoint, but it uses the additional information contained in events which lie far from the endpoint. We found the mass by comparing the HERWIG generated m_2C distribution to ideal distributions for different masses. We find that for the case studied, with 100 fb^-1 of integrated luminosity (about 400 signal events), the invisible particle's mass can be measured to a precision of 4.1 GeV. We conclude that this technique's precision and accuracy is as good as, if not better than, the best known techniques for invisible-particle mass-determination at hadron colliders.Comment: 20 pages, 11 figures, minor correction

The race for supersymmetry: using mT2 for discovery

We describe how one may employ a very simple event selection, using only the kinematic variable mT2, to search for new particles at the LHC. The method is useful when searching for evidence of models (such as R-parity conserving supersymmetry) which have a Z2 parity and a weakly-interacting lightest parity-odd particle. We discuss the kinematic properties which make this variable an excellent discriminant against the great majority of Standard Model backgrounds. Monte Carlo simulations suggest that this approach could be used to discover supersymmetry with somewhat smaller integrated luminosities (or perhaps lower center-of-mass energies) than would be required for other comparable analyses.Comment: 8 page

Finding Higgs bosons heavier than 2 m_W in dileptonic W-boson decays

We reconsider observables for discovering a heavy Higgs boson (with m_h > 2m_W) via its di-leptonic decays h -> WW -> l nu l nu. We show that observables generalizing the transverse mass that take into account the fact that both of the intermediate W bosons are likely to be on-shell give a significant improvement over the variables used in existing searches. We also comment on the application of these observables to other decays which proceed via narrow-width intermediates.Comment: v1:4 pages, 1 figure; v2: 6 pages, 2 figures, substantially revise

Di-Higgs final states augMT2ed – Selecting hh events at the high luminosity LHC

Higgs boson self-interactions can be investigated via di-Higgs (pp→hh+X) production at the LHC. With a small O(30) fb Standard Model production cross section, and a large View the MathML source background, this measurement has been considered challenging, even at a luminosity-upgraded LHC. We demonstrate that by using simple kinematic bounding variables, of the sort already employed in existing LHC searches, the dominant View the MathML source background can be largely eliminated. Simulations of the signal and the dominant background demonstrate the prospect for measurement of the di-Higgs production cross section at the 30% level using 3 ab−1 of integrated luminosity at a high luminosity LHC. This corresponds to a Higgs self-coupling determination with 60% accuracy in the View the MathML source mode, with potential for further improvements from e.g. subjet technologies and from additional di-Higgs decay channels

A Storm in a "T" Cup

We revisit the process of transversification and agglomeration of particle momenta that are often performed in analyses at hadron colliders, and show that many of the existing mass-measurement variables proposed for hadron colliders are far more closely related to each other than is widely appreciated, and indeed can all be viewed as a common mass bound specialized for a variety of purposes.Comment: 3 pages, 2 figures, presented by K.C. Kong at the 19th Particles and Nuclei International Conference, PANIC 2011, MIT, Cambridge, MA (July 24-29, 2011